Rotary internal combustion engine with pilot subchamber

ABSTRACT

A non-Wankel rotary engine having an insert in the peripheral wall of the outer body, the insert being made of a material having a greater heat resistance than that of the peripheral wall, having a subchamber defined therein and having an inner surface bordering the cavity, the subchamber communicating with the cavity through at least one opening defined in the inner surface and having a shape forming a reduced cross-section adjacent the opening, a pilot fuel injector having a tip received in the subchamber, an ignition element having a tip received in the subchamber, and a main fuel injector extending through the housing and having a tip communicating with the cavity at a location spaced apart from the insert.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/750,523 filed Jan. 25, 2013, which is a continuation-in-part of U.S.application Ser. No. 13/273,534 filed Oct. 14, 2011, which claimspriority from provisional U.S. application No. 61/512,593 filed Jul. 28,2011, the entire contents of all of which are incorporated by referenceherein.

TECHNICAL FIELD

The application relates generally to a rotary internal combustionengine.

BACKGROUND OF THE ART

Rotary engines, such as for example Wankel engines, use the rotation ofa piston to convert pressure into a rotating motion, instead of usingreciprocating pistons. In these engines, the rotor typically includes anumber of seals that remain in contact with a peripheral wall of therotor cavity of the engine throughout the rotational motion of the rotorto create a plurality of rotating chambers when the rotor rotates.

Rotary engines come in many forms. One well-known type, the Wankelengine, has a generally triangular rotor received in a two-lobedepitrochoid cavity. Other non-Wankel rotary engines types exist as well.However, known arrangements are not optimized, in terms of combustionarrangements and characteristics, and thus room for improvement exists.

SUMMARY

In one aspect, there is provided a non-Wankel rotary engine comprisingan outer body having an internal cavity defined by two axially spacedapart end walls and a peripheral wall extending between the end walls, arotor body rotatable within the cavity in sealing engagement with theperipheral wall and defining at least one chamber of variable volume inthe cavity around the rotor body, an insert in the peripheral wall ofthe outer body, the insert being made of a material having a greaterheat resistance than that of the peripheral wall, the insert having asubchamber defined therein and having an inner surface bordering thecavity, the subchamber communicating with the cavity through at leastone opening defined in the inner surface and having a shape forming areduced cross-section adjacent the opening, a pilot fuel injector havinga tip received in the subchamber, an ignition element having a tipreceived in the subchamber, and a main fuel injector extending throughthe outer body and having a tip communicating with the cavity at alocation spaced apart from the insert.

In another aspect, there is provided an outer body for a non-Wankelrotary engine comprising two axially spaced apart end walls, aperipheral wall extending between the end walls and defining an internalcavity therewith for receiving a rotor therein, an insert in theperipheral wall of the outer body, the insert being made of a materialhaving a greater heat resistance than that of the peripheral wall, theinsert having a subchamber defined therein and having an inner surfacebordering the cavity, the subchamber communicating with the cavitythrough at least one opening defined in the inner surface and having ashape forming a reduced cross-section adjacent the opening, at least oneof the insert and the peripheral wall having a pilot fuel injectorelongated hole defined therethrough communicating with the subchamberand sized to receive a pilot fuel injector therein, at least one of theinsert and the peripheral wall having an ignition element elongated holedefined therethrough communicating with the subchamber and sized toreceive an ignition element therein, and the peripheral wall having amain fuel injector elongated hole defined therethrough spaced apart fromthe insert and sized to receive a main fuel injector therein.

In yet another aspect, there is provided a method of injecting fuel intoa non-Wankel rotary engine having rotating chambers each having a volumevarying between a minimum volume and a maximum volume, the methodcomprising injecting a minor portion of the fuel into a subchamberdefined adjacent to and in sequential communication with each of therotating chambers and having a subchamber volume corresponding to from5% to 25% of a sum of the minimum volume and the subchamber volume,igniting the fuel within the subchamber, partially restricting a flow ofthe ignited fuel from the subchamber to the rotating chambers, andinjecting a remainder of the fuel into each of the rotating chamberssequentially, independently of and spaced apart from the subchamber.

In a further aspect, there is provided a rotary engine comprising: anouter body made of heat resistant material having a greater heatresistance than aluminium, the body having an internal cavity defined bytwo axially spaced apart end walls and a peripheral wall extendingbetween the end walls, the cavity having an epitrochoid shape definingtwo lobes; a rotor body having three circumferentially spaced apexportions, the rotor body being engaged to an eccentric portion of ashaft to rotate and perform orbital revolutions within the cavity witheach of the apex portions remaining in sealing engagement with theperipheral wall and separating three rotating chambers of variablevolume defined in the cavity around the rotor body; a subchamberintegrally defined in the peripheral wall of the outer body andcommunicating with the cavity through at least one opening defined inthe peripheral wall, the subchamber having a shape forming a reducedcross-section adjacent the opening; a pilot fuel injector hole definedthrough the outer body for receiving a fuel injector and incommunication with the subchamber; an ignition element hole definedthrough the outer body for receiving an ignition element and incommunication with the subchamber; and a main fuel injector hole definedthrough the outer body and in communication with the cavity at alocation spaced apart from the subchamber.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 is a partial, schematic cross-sectional view of a rotary internalcombustion engine in accordance with a particular embodiment;

FIG. 2 is a schematic cross-sectional view of an insert of the engine ofFIG. 1;

FIG. 3 is a schematic cross-sectional view of an insert in accordancewith another embodiment;

FIG. 4 is a schematic cross-sectional view of an insert in accordancewith a further embodiment;

FIG. 5 is a schematic cross-sectional view of a rotary internalcombustion engine in accordance with another embodiment;

FIG. 6 is a schematic cross-sectional view of a rotary internalcombustion engine in accordance with another embodiment;

FIG. 7 is a schematic cross-sectional view of a rotary internalcombustion engine in accordance with another embodiment; and

FIG. 8 is a schematic cross-sectional view of a rotary internalcombustion engine in accordance with another embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, a rotary internal combustion engine 10 known as aWankel engine is schematically and partially shown. In a particularembodiment, the rotary engine 10 is used in a compound cycle enginesystem such as described in Lents et al.'s U.S. Pat. No. 7,753,036issued Jul. 13, 2010 or as described in Julien et al.'s U.S. Pat. No.7,775,044 issued Aug. 17, 2010, the entire contents of both of which areincorporated by reference herein. The compound cycle engine system maybe used as a prime mover engine, such as on an aircraft or othervehicle, or in any other suitable application. In any event, in such asystem, air is compressed by a compressor before entering the Wankelengine, and the engine drives one or more turbine(s) of the compoundengine. In another embodiment, the rotary engine 10 is used without aturbocharger, with air at atmospheric pressure.

The engine 10 comprises an outer body 12 having axially-spaced end walls14 with a peripheral wall 18 extending therebetween to form a rotorcavity 20. The inner surface 19 of the peripheral wall 18 of the cavity20 has a profile defining two lobes, which is preferably an epitrochoid.

An inner body or rotor 24 is received within the cavity 20, with thegeometrical axis of the rotor 24 being offset from and parallel to theaxis of the outer body 12. The rotor 24 has axially spaced end faces 26adjacent to the outer body end walls 14, and a peripheral face 28extending therebetween. The peripheral face 28 defines threecircumferentially-spaced apex portions 30 (only one of which is shown),and a generally triangular profile with outwardly arched sides. The apexportions 30 are in sealing engagement with the inner surface ofperipheral wall 18 to form three rotating working chambers 32 (only twoof which are partially shown) between the inner rotor 24 and outer body12. A recess 38 is defined in the peripheral face 28 of the rotor 24between each pair of adjacent apex portions 30, to form part of thecorresponding chamber 32.

The working chambers 32 are sealed. Each rotor apex portion 30 has anapex seal 52 extending from one end face 26 to the other and protrudingradially from the peripheral face 28. Each apex seal 52 is biasedradially outwardly against the peripheral wall 18 through a respectivespring. An end seal 54 engages each end of each apex seal 52, and isbiased against the respective end wall 14 through a suitable spring.Each end face 26 of the rotor 24 has at least one arc-shaped face seal60 running from each apex portion 30 to each adjacent apex portion 30,adjacent to but inwardly of the rotor periphery throughout its length. Aspring urges each face seal 60 axially outwardly so that the face seal60 projects axially away from the adjacent rotor end face 26 intosealing engagement with the adjacent end wall 14 of the cavity. Eachface seal 60 is in sealing engagement with the end seal 54 adjacent eachend thereof.

Although not shown in the Figures, the rotor 24 is journaled on aneccentric portion of a shaft and includes a phasing gear co-axial withthe rotor axis, which is meshed with a fixed stator phasing gear securedto the outer body co-axially with the shaft. The shaft rotates the rotor24 and the meshed gears guide the rotor 24 to perform orbitalrevolutions within the rotor cavity. The shaft rotates three times foreach complete rotation of the rotor 24 as it moves around the rotorcavity 20. Oil seals are provided around the phasing gear to preventleakage flow of lubricating oil radially outwardly thereof between therespective rotor end face 26 and outer body end wall 14.

At least one inlet port (not shown) is defined through one of the endwalls 14 or the peripheral wall 18 for admitting air (atmospheric orcompressed) into one of the working chambers 32, and at least oneexhaust port (not shown) is defined through one of the end walls 14 orthe peripheral wall 18 for discharge of the exhaust gases from theworking chambers 32. The inlet and exhaust ports are positioned relativeto each other and relative to the ignition member and fuel injectors(further described below) such that during each rotation of the rotor24, each chamber 32 moves around the cavity 20 with a variable volume toundergo the four phases of intake, compression, expansion and exhaust,these phases being similar to the strokes in a reciprocating-typeinternal combustion engine having a four-stroke cycle.

In a particular embodiment, these ports are arranged such that therotary engine 10 operates under the principle of the Miller or Atkinsoncycle, with its volumetric compression ratio lower than its volumetricexpansion ratio. In another embodiment, the ports are arranged such thatthe volumetric compression and expansion ratios are equal or similar toone another.

As described further below, a pilot subchamber 72 is defined in theouter body 12, for pilot fuel injection and ignition. In this example,the pilot subchamber 72 is provided in an insert 34 received in acorresponding hole 36 defined through the peripheral wall 18 of theouter body 12, for pilot fuel injection and ignition. The peripheralwall 18 also has a main injector elongated hole 40 defined therethrough,in communication with the rotor cavity 20 and spaced apart from theinsert 34. A main fuel injector 42 is received and retained within thiscorresponding hole 40, with the tip 44 of the main injector 42communicating with the cavity 20 at a point spaced apart from the insert34. The main injector 42 is located rearwardly of the insert 34 withrespect to the direction R of the rotor rotation and revolution, and isangled to direct fuel forwardly into each of the rotating chambers 32sequentially with a tip hole pattern designed for an adequate spray.

Referring particularly to FIG. 2, in this example the insert includes anelongated body 46 extending across a thickness of the peripheral wall18, with an enlarged flange 48 at its outer end which is biased awayfrom a shoulder 50 defined in the peripheral wall 18, and against agasket (not shown) made of an appropriate type of heat resistantmaterial such as a silica based material. A washer 56, such as forexample a steel or titanium washer, and spring 58, such as for example awave spring or a Belleville spring, are provided between the flange 48and the shoulder 50 of the peripheral wall 18. The spring 58 biases thebody 46 against a cover 62 having a cross-section greater than that ofthe hole 36 and extending over an outer surface 64 of the peripheralwall 18. The cover 62 is connected to the peripheral wall 18, forexample through brazing. Alternate types of connections can also beused, including but not limited to a connection through fasteners suchas bolts, to help facilitate replacement of the insert if necessary.

The insert body 46 has an inner surface 66 which is continuous with theinner surface 19 of the peripheral wall 20 to define the cavity 20. Theinsert hole 36 in the wall 18 defines a flange 68 extending in theinsert hole 36 adjacent the inner surface 19, and the inner end of theinsert body 46 is complementarily shaped to engage this flange 68, witha gasket 70 being received therebetween.

In this example, the insert body 46 is made of a material having agreater heat resistance than that of the peripheral wall 18, which in aparticular embodiment is made of aluminium. In this particularembodiment, the insert body 46 is made of an appropriate type ofceramic.

The insert body 46 has a pilot subchamber 72 defined therein incommunication with the rotor cavity 20. In the embodiment shown, thesubchamber 72 has a circular cross-section; alternate shapes are alsopossible. The subchamber 72 communicates with the cavity through atleast one opening 74 defined in the inner surface 66. The subchamber 72has a shape forming a reduced cross-section adjacent the opening 74,such that the opening 74 defines a restriction to the flow between thesubchamber 72 and the cavity 20. The opening 74 may have various shapesand/or be defined by a pattern of multiple holes. As can be seen in FIG.2, the opening 74 has an area smaller than the maximum cross-sectionalarea of the subchamber 72, which is defined spaced apart from theopening 74.

The peripheral wall 18 has a pilot injector elongated hole 76 definedtherethrough in proximity of the insert 34, extending at a non-zeroangle with respect to a surface of an outer wall of the insert 34 andwith respect to the longitudinal direction of the insert (which in theembodiment shown corresponds to the direction of the transverse axis Tof the outer body 12). The pilot injector hole 76 is in communicationwith the subchamber 72. A pilot fuel injector 78 is received andretained within the corresponding hole 76, with the tip 80 of the pilotinjector 78 being received in the subchamber 72. As can be seen in FIG.2, the insert body 46 has an injector opening defined therethroughproviding the communication between the pilot injector elongated hole 76and the subchamber 72, and the tip 80 of the pilot injector 78 isreceived in the subchamber 72 through this injector opening, with amajor part of the pilot injector 78 being received in the pilot injectorelongated hole 76 outside of the insert 34. The opening providing thecommunication between the pilot injector elongated hole 76 and thesubchamber 72 has an area smaller than the maximum cross-sectional areaof the subchamber 72.

The insert body 46 and cover 62 have an ignition element elongated hole82 defined therein extending along the direction of the transverse axisT of the outer body 12, also in communication with the subchamber 72. Ascan be seen in FIG. 2, the ignition element elongated hole 82 and thesubchamber 72 communicate through an opening having an area smaller thanthe maximum cross-sectional area of the subchamber 72. An ignitionelement 84 is received and retained within the corresponding hole 82,with the tip 86 of the ignition element 84 being received in thesubchamber 72. In the embodiment shown, the ignition element 84 is aglow plug. Alternate types of ignition elements 84 which may be usedinclude, but are not limited to, plasma ignition, laser ignition, sparkplug, microwave, etc.

The pilot injector 78 and main injector 42 inject fuel, which in aparticular embodiment is heavy fuel e.g. diesel, kerosene (jet fuel),equivalent biofuel, etc. into the chambers 32. Alternately, the fuel maybe any other adequate type of fuel suitable for injection as described,including non-heavy fuel such as for example gasoline or liquid hydrogenfuel. In a particular embodiment, at least 0.5% and up to 20% of thefuel is injected through the pilot injector 78, and the remainder isinjected through the main injector 42. In another particular embodiment,at most 10% of the fuel is injected through the pilot injector 78. Inanother particular embodiment, at most 5% of the fuel is injectedthrough the pilot injector 78. The main injector 42 injects the fuelsuch that each rotating chamber 32 when in the combustion phase containsa lean mixture of air and fuel.

Referring to FIG. 3, an insert 134 according to another embodiment isshown, engaged to the same outer body 12. The insert 134 extends acrossa thickness of the peripheral wall 18, and includes an inner bodyportion 146 and an outer body portion 162 which are attached together,for example through a high temperature braze joint 188. The outer bodyportion 162 has an enlarged flange 148 at its outer end which abuts theouter surface 64 of the peripheral wall 18 and is connected thereto, forexample through bolts with appropriate sealing such as a gasket or crushseal (not shown). Alternate types of connections can also be used,including but not limited to a brazed connection.

The inner body portion 146 has an inner surface 166 which is continuouswith the inner surface 19 of the peripheral wall 18 to define the cavity20. The inner end of the inner body portion 146 is complementarilyshaped to engage the flange 68 extending in the insert hole 36 adjacentthe inner surface 19, with a gasket 70 being received therebetween.

In this particular embodiment, the body portions 146, 162 are made of anappropriate type of super alloy such as a Nickel based super alloy.

The pilot subchamber 72 is defined in the insert 134 at the junctionbetween the body portions 146, 162, with the inner body portion 146defining the opening 74 for communication between the subchamber 72 andthe cavity 20. The outer body portion 162 has the ignition elementelongated hole 82 defined therein along the direction of the transverseaxis T and in communication with the subchamber 72. The ignition element84 is received and retained within the corresponding hole 82, forexample through threaded engagement. As in the previous embodiment, thetip 86 of the ignition element 84 is received in the subchamber 72.

Referring to FIG. 4, an insert 234 according to another embodiment isshown. The insert 234 is received in a corresponding hole 236 definedthrough the peripheral wall 18. The insert 234 includes an inner bodyportion 246 and an outer body portion 262 which are attached together,for example through a high temperature braze joint, with the subchamber72 being defined at the junction of the two portions 246, 262. The innerbody portion 246 defines the opening 74 for communication between thesubchamber 72 and the cavity 20.

The outer body portion 262 has the ignition element elongated hole 82defined therethrough in communication with the subchamber 72. The outerbody portion 262 includes an inner enlarged section 245 connected to theinner body portion 246 and defining the subchamber 72. The enlargedsection 245 extends substantially across the width of the hole 236around the subchamber 72, then tapers to a reduced width section 247extending therefrom. The reduced width section 247 has at its outer endan enlarged flange 248 which abuts a shoulder 250 defined in the outersurface 64 of the peripheral wall 18 around the hole 236. An outersection 249, which in the embodiment shown has a width intermediate thatof the sections 245 and 247, extends outwardly from the flange 248. Theflange is connected to the shoulder, for example through bolts (notshown) with appropriate sealing such as a crush seal or a gasket (notshown) made of high temperature material, for example a silica basedmaterial or grafoil, between the flange 248 and shoulder 250. Alternatetypes of connections can also be used.

The inner body portion 246 has an inner surface 266 which is continuouswith the inner surface 19 of the peripheral wall 18 to define the cavity20. The inner body portion 246 includes a groove defined therearoundnear the inner surface 266, in which an appropriate seal 251, forexample a silica based gasket tape, is received in contact with thewalls of the insert hole 236. In this embodiment, the walls of theinsert holes 236 are straight adjacent the inner surface 19, i.e. thereis no flange adjacent the inner surface 19.

The volume of the subchamber 72 in the insert 34, 134, 234 is selectedto obtain a stoichiometric mixture around ignition within an acceptabledelay, with some of the exhaust product from the previous combustioncycle remaining in the subchamber 72. In a particular embodiment, thevolume of the subchamber 72 is at least 0.5% and up to 3.5% of thedisplacement volume, with the displacement volume being defined as thedifference between the maximum and minimum volumes of one chamber 32. Inanother particular embodiment, the volume of the subchamber 72corresponds to from about 0.625% to about 1.25% of the displacementvolume.

The volume of the subchamber 72 may also be defined as a portion of thecombustion volume, which is the sum of the minimum chamber volumeV_(min) (including the recess 38) and the volume of the subchamber V₂itself. In a particular embodiment the subchamber 72 has a volumecorresponding to from 5% to 25% of the combustion volume, i.e. V₂=5% to25% of (V₂+V_(min)). In another particular embodiment, the subchamber 72has a volume corresponding to from 10% to 12% of the combustion volume,i.e. V₂=10% to 12% of (V₂+V_(min)).

The subchamber 72 may help create a stable and powerful ignition zone toignite the overall lean main combustion chamber 32 to create thestratified charge combustion. The subchamber 72 may improve combustionstability, particularly but not exclusively for a rotary engine whichoperates with heavy fuel below the self ignition of fuel. The insert 34,134, 234 made of a heat resistant material may advantageously create ahot wall around the subchamber which may further help with ignitionstability.

The teachings herein are applicable to many rotary engine types, and notjust Wankel engines. Therefore, in another embodiment, the rotary enginewith subchamber the 72 may be a non-Wankel engine. A “non-Wankel”engine, as used in this description and the appended claims, means arotary engine suitable for use with the present invention, but excludingWankel type engines.

In a particular embodiment, the rotary engine may be a single oreccentric type rotary engine in which the rotor rotates about a fixedcenter of rotation. For example, the rotary engine may be a sliding vaneengine, such as described in U.S. Pat. No. 5,524,587 issued Jun. 11,1996 or in U.S. Pat. No. 5,522,356 issued Jun. 4, 1996, the entirecontents of both of which are incorporated by reference herein.

Referring to FIG. 5, an example of a sliding vane engine 100 is shown.The engine 100 includes an outer body 112 defining a rotor cavity 20receiving a rotor 124 having a number of vanes 125. The rotor 124includes an inner hub assembly 127 rotating about a first axis and anouter hub assembly 129 rotating about a second axis offset from thefirst axis, with the two hub assemblies 127, 129 being mechanicallylinked. The vanes 125 are pivotally connected to the inner hub assembly127 and are slidingly engaged through slots defined between adjacentsections of the outer hub assembly 129. The sections of the outer hubassembly 129 are thus sealingly engaged to the vanes 125 at differentdistances from the first axis of the inner hub assembly 127, defining aplurality of chambers 32 of variable volume within the cavity 20 aroundthe rotor 124.

In the embodiment shown, the engine 100 includes the subchamber 72described above, in this example defined in the insert 34 received in ahole 36 of a peripheral wall 118 of the outer body 112. The peripheralwall 118 also has a main injector elongated hole 40 definedtherethrough, in communication with the rotor cavity 20 and spaced apartfrom the insert 34. The insert is biased against the cover 62 retainingthe insert 34 within the hole 36. The insert 34 is made of a materialhaving a greater heat resistance than that of the peripheral wall 18 anddefines the pilot subchamber 72 in communication with the rotor cavity20 through at least one opening 74. The peripheral wall 118 and/or theinsert 34 has the pilot injector elongated hole 76 and the ignitionelement elongated hole 82 defined therethrough in communication with thesubchamber 72. Other embodiments may be provided for the insert in theengine 100, including, but not limited to, the other inserts 134, 234described above.

In another particular embodiment, the rotary engine may be anoscillatory rotating engine, including two or more rotors rotating atdifferent angular velocities, causing the distance between portions ofthe rotors to vary and as such the chamber volume to change. Referringto FIG. 6, an example of such an engine is shown. The engine 200includes an inner rotor 224 and an outer body or rotor 212 rotating atdifferent angular velocities, the outer rotor 212 defining a rotorcavity 20 in which the inner rotor 212 is received. Chambers 32 ofvariable volume are defined within the cavity 20 around the inner rotor224.

In the embodiment shown, the engine 200 includes the subchamber 72described above, in this example defined in the insert 34 received in ahole 36 of a peripheral wall 218 of the outer body 212. The peripheralwall 218 also has the main injector elongated hole 40 definedtherethrough spaced apart from the insert 34, and the peripheral wall218 and/or the insert 34 has the pilot injector elongated hole 76 andthe ignition element elongated hole 82 defined therethrough. Otherembodiments may be provided for the insert in the engine 200, including,but not limited to, the other inserts 134, 234 described above.

In another particular embodiment, the rotary engine is a planetaryrotating engine having a different geometry than that of the Wankelengine. Referring to FIG. 7, an example of such an engine is shown. Theengine 300 includes an outer body 312 forming a rotor cavity 20 with aperipheral inner surface 319 thereof having an epitrochoid profiledefining three lobes. The engine 300 also includes a rotor 324 with fourapex portions 330 in sealing engagement with the peripheral innersurface 319 to form four rotating working chambers 32 of variable volumewithin the cavity 20 around the rotor 324. The rotor 324 is journaled onan eccentric portion of a shaft and performs orbital revolutions withinthe cavity 20.

In the embodiment shown, the engine 300 includes the subchamber 72described above, in this example defined in the insert 34 received in ahole 36 of a peripheral wall 318 of the outer body 312. The peripheralwall 318 also has the main injector elongated hole 40 definedtherethrough spaced apart from the insert 34, and the peripheral wall318 and/or the insert 34 has the pilot injector elongated hole 76 andthe ignition element elongated hole 82 defined therethrough. Otherembodiments may be provided for the insert in the engine 300, including,but not limited to, the other inserts 134, 234 described above.

The subchamber 72 may be provided integrally within the outer body 12,112, 212, 312 of the engine 10, 100, 200, 300, provided the outer body12, 112, 212, 312 is made of a material having adequate heat resistanceand such other properties required to provide a suitable outer body.Referring to FIG. 8, the Wankel engine 10 is shown with the subchamber72, pilot injector hole 76 and ignition element hole 82 integrallydefined in the outer body 12, more particularly in the peripheral wall18. In a particular embodiment, the outer body 12 is made of a materialhaving a heat resistance greater than that of aluminium. In a particularembodiment, the outer body 12 is made of an appropriate type of ceramicor of an appropriate type of super alloy, such as for example a Nickelbased super alloy. Though not shown, a wear insert may be provided inrotor cavity 20 for contacting the rotor sliding surfaces. The integralsubchamber may be applied to any of the rotary engine configurationscontemplated by the present description.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the invention(s)disclosed. For example, the mechanical arrangements of the rotaryengines described above are merely examples of many possibleconfigurations which are suitable for use with the present invention(s).Any suitable injector configuration and arrangement may be used. Hence,modifications which fall within the scope of the present invention willbe apparent to those skilled in the art, in light of a review of thisdisclosure, and such modifications are intended to fall within theappended claims.

The invention claimed is:
 1. A non-Wankel rotary engine comprising: anouter body having an internal cavity defined by two axially spaced apartend walls and a peripheral wall extending between the end walls; a rotorbody rotatable within the cavity in sealing engagement with theperipheral wall and defining at least one chamber of variable volume inthe cavity around the rotor body; an insert in the peripheral wall ofthe outer body, the insert being made of a material having a greaterheat resistance than that of the peripheral wall, the insert having asubchamber defined therein and having an inner surface bordering thecavity, the subchamber communicating with the cavity through at leastone opening defined in the inner surface and having a shape forming areduced cross-section adjacent the opening; a pilot fuel injector havinga tip received in the subchamber; an ignition element having a tipreceived in the subchamber; and a main fuel injector extending throughthe outer body and having a tip communicating with the cavity at alocation spaced apart from the insert.
 2. The engine as defined in claim1, wherein the volume of one of the at least one chamber varies betweena minimum volume and a maximum volume with a difference between themaximum volume and the minimum volume defining a displacement volume,the subchamber having a volume of at least about 0.5% of thedisplacement volume and at most about 3.5% of the displacement volume.3. The engine as defined in claim 1, wherein the rotor body rotatesabout a fixed axis of rotation.
 4. The engine as defined in claim 1,wherein the at least one chamber includes a plurality of chambers, andthe rotor body includes sliding vanes defining the chambers.
 5. Theengine as defined in claim 1, wherein the rotor body is engaged to aneccentric portion of a shaft to rotate and perform orbital revolutions.6. The engine as defined in claim 1, wherein the volume of one of the atleast one chamber varies between a minimum volume and a maximum volume,the subchamber having a volume corresponding to from 5% to 25% of a sumof the minimum volume and the volume of the subchamber.
 7. The engine asdefined in claim 1, wherein the insert is made of ceramic or superalloy.
 8. The engine as defined in claim 1, wherein the pilot fuelinjector extends through the peripheral wall at an angle with respect tothe insert with only a portion thereof extending within the insert. 9.The engine as defined in claim 1, further comprising a heavy fuel sourcein communication with the fuel injectors.
 10. An outer body for anon-Wankel rotary engine comprising: two axially spaced apart end walls;a peripheral wall extending between the end walls and defining aninternal cavity therewith for receiving a rotor therein; an insert inthe peripheral wall of the outer body, the insert being made of amaterial having a greater heat resistance than that of the peripheralwall, the insert having a subchamber defined therein and having an innersurface bordering the cavity, the subchamber communicating with thecavity through at least one opening defined in the inner surface andhaving a shape forming a reduced cross-section adjacent the opening; atleast one of the insert and the peripheral wall having a pilot fuelinjector elongated hole defined therethrough communicating with thesubchamber and sized to receive a pilot fuel injector therein; at leastone of the insert and the peripheral wall having an ignition elementelongated hole defined therethrough communicating with the subchamberand sized to receive an ignition element therein; and the peripheralwall having a main fuel injector elongated hole defined therethroughspaced apart from the insert and sized to receive a main fuel injectortherein.
 11. The outer body as defined in claim 10, wherein the insertis made of ceramic or super alloy.
 12. The outer body as defined inclaim 10, wherein the peripheral wall has a major part of the pilot fuelinjector elongated hole defined therethrough.
 13. The outer body asdefined in claim 10, wherein only the insert has the ignition elementelongated hole defined therethrough.
 14. A method of injecting fuel intoa non-Wankel rotary engine having rotating chambers each having a volumevarying between a minimum volume and a maximum volume, the methodcomprising: injecting a minor portion of the fuel into a subchamberdefined adjacent to and in sequential communication with each of therotating chambers and having a subchamber volume corresponding to from5% to 25% of a sum of the minimum volume and the subchamber volume;igniting the fuel within the subchamber; partially restricting a flow ofthe ignited fuel from the subchamber to the rotating chambers; andinjecting a remainder of the fuel into each of the rotating chamberssequentially, independently of and spaced apart from the subchamber. 15.The method as defined in claim 14, wherein injecting a minor portion ofthe fuel into the subchamber includes injecting from 0.5% to 20% of thefuel.
 16. The method as defined in claim 14, wherein the fuel is heavyfuel.
 17. The method as defined in claim 14, wherein injecting the minorportion of the fuel is done into the subchamber with the subchambervolume corresponding to from 10% to 12% of the sum of the minimum volumeand the subchamber volume.
 18. The method as defined in claim 14,wherein injecting the minor portion of the fuel is done through aninsert in a peripheral wall of the engine, with the subchamber beingdefined within the insert.
 19. The method as defined in claim 14,wherein injecting the minor portion of the fuel is done in an angleddirection with respect to a central transverse axis of an outer body ofthe engine.
 20. The method as defined in claim 14, further comprisinghelping combustion with a hot wall around the subchamber by providingthe subchamber in an insert made of a material more resistant to hightemperature that a remainder of an outer body of the engine.